What is Glaucoma?
Glaucoma is actually a group of eye diseases that damage the optic nerve usually due to increased pressure in the eye. The optic nerve, located at the back of the eye, carries information from the eye to the brain, and when the nerve is damaged, vision is lost.
At first, most people with glaucoma lose side (peripheral) vision. But if the disease is not treated in time, vision loss may worsen and can lead to total blindness.
Who is at risk for Glaucoma?
Everyone is at risk for glaucoma, but certain groups are at higher risk.
Age: People Over 40
Glaucoma is much more common among older people, the risk rises after 40. You are six times more likely to get glaucoma if you are over 60 years old.
Family Members with Glaucoma
The most common type of glaucoma, primary open-angle glaucoma, is often hereditary. If your parents or siblings have glaucoma, that increases your risk of glaucoma four to nine times.
Glaucoma is the leading cause of blindness among African Americans and people of African descent. Glaucoma is six to eight times more common in African Americans than in Caucasians.
The risk for Hispanic population is greater than those of predominantly European ancestry, and that risk increases over age 60.
People of Asian descent appear to be at increased risk for angle-closure glaucoma. People of Japanese descent are at higher risk for normal-tension glaucoma.
Other Risk Factors
- High myopia (nearsightedness)
- Central corneal thickness less than 0.5 mm
- Sleep apnea
- Steroid use
- Eye injury
People at high risk for glaucoma should get a complete eye exam, including dilation, every year. Finding and treating glaucoma early is important to prevent blindness. If you are at high risk for the disease, be sure to get checked by an ophthalmologist even if you have no symptoms.
What causes Glaucoma?
The cause of glaucoma generally is a failure of the eye to maintain an appropriate balance between the amount of internal (intraocular) fluid produced and the amount that drains away. The buildup of fluid causes high eye pressure that pushes against the optic nerve until nerve fibers are permanently damaged and vision is lost.
Underlying reasons for this imbalance usually relate to the actual type of glaucoma.
What are the types of Glaucoma?
There are several types of glaucoma, but the mechanisms causing high intraocular pressure fall into two categories:
- Open-angle glaucoma is the most common form. In this type of glaucoma, the internal drainage system (trabecular meshwork) appears open, but there is poor flow through the drainage channels. Usually high pressure builds up, and over a period of years, causes optic nerve damage that slowly leads to loss of eyesight. One eye may be affected earlier than the other. Much eyesight may be lost before it is noticed.
- Narrow-angle glaucoma is less common. In this type of glaucoma, the cornea (transparent front of the eye), the iris (colored part of the eye) and the lens (behind the iris) are situated too close to each other, causing blockage of the movement of fluid within the eye and leading to increased intraocular pressure.
Narrow angles can lead to a sudden rapid rise of pressure - acute angle closure glaucoma - which is an emergency. Acute angle closure glaucoma requires medical care right away to prevent permanent damage and vision loss.
Most glaucoma happens as people get older. However, sometimes children and young adults can also get a type of the disease (juvenile glaucoma). Rarely, glaucoma can be present at or soon after birth, usually due to defects in the development of the eye (congenital glaucoma).
What are the Symptoms of Glaucoma?
Symptoms of Open-angle Glaucoma
There are typically no early warning signs or symptoms in open-angle glaucoma. It develops slowly and sometimes without noticeable loss of sight for many years.
Most people who have open-angle glaucoma feel fine and do not notice a change in their vision because the initial loss of vision is only side or peripheral vision, and their central visual acuity and sharpness of vision is maintained until late in the disease.
By the time a patient is aware of vision loss, the disease is usually quite advanced. Vision loss from glaucoma is not reversible with treatment or even with surgery. All treatment is aimed at preventing further vision loss, so early diagnosis is very important.
Symptoms of Narrow-angle Glaucoma
Very often, patients with narrow angles do not have symptoms. Sometimes they may have headaches in the evenings or after prolonged near work, which may be associated with blurred vision or seeing colored halos around lights.
Symptoms of Angle-Closure Glaucoma
In patients with narrow angles, sometimes the internal drainage may get completely blocked resulting in a sudden rapid rise in eye pressure. Symptoms include:
- Hazy or blurred vision
- The appearance of rainbow-colored circles around bright lights
- Severe eye and head pain
- Nausea or vomiting (accompanying severe eye pain)
- Sudden sight loss
This is an EMERGENCY and demands immediate medical attention.
How is Glaucoma Treated?Glaucoma can be treated with eye drops, laser surgery, traditional surgery or a combination of these methods. The goal of all glaucoma treatment is to prevent loss of vision. Vision loss from glaucoma is irreversible, but glaucoma can be managed if detected early. With medical and/or surgical treatment, most people with glaucoma will not lose their sight.
Taking medications regularly, as prescribed, is crucial to preventing vision-threatening damage. While every drug has some potential side effects, most patients experience no side effects at all.
Since eye drops are absorbed into the bloodstream, tell your doctor about all medications you are currently taking. To minimize absorption into the bloodstream and maximize the amount of drug absorbed in the eye, close your eye for five minutes after administering the drops - this closes the tear ducts which drain into the nose and allows more of the medication to enter the eye. While many eye drops cause some burning or a stinging sensation at first, the discomfort should last for only a few seconds.
When medications do not achieve the desired results, or have intolerable side effects, or are too expensive, laser treatment can be considered.
Evidence supports the use of laser as primary treatment before the use of any eye drops, as the pressure lowering effect of laser seems to be greater when no drops have been used. Complications from laser are minimal.
Laser procedures take only a few minutes and can be performed in either a doctor's office or an outpatient facility. You may go home and resume your normal activities following surgery.
Selective Laser Trabeculoplasty (SLT) -- for open-angle glaucoma
SLT is a laser that uses very low levels of energy. It is termed "selective" since it leaves the trabecular meshwork intact, targeting only cells containing pigment. The eye's drainage system is changed in very subtle ways so that aqueous fluid is able to pass more easily out of the drain, thus lowering IOP.
It usually takes a few weeks to see the full pressure-lowering effect of this procedure, during which time it is necessary to continue taking medications. However, most patients are eventually able to discontinue some of their medications.
SLT, unlike previous types of laser surgery, may be safely repeated. Current research indicates that repeat applications of SLT, or even SLT after prior ALT, effectively lowers IOP.
Argon Laser Trabeculoplasty (ALT) -- for open-angle glaucoma
The laser treats the trabecular meshwork of the eye, increasing the drainage outflow, thereby lowering the IOP. In many cases, medication will still be needed. Argon laser trabeculoplasty though successful, can be performed only two to three times in each eye over a lifetime.
Laser Peripheral Iridotomy (LPI) -- for angle-closure glaucoma
This procedure is used to make a small opening through the iris, allowing aqueous fluid to flow from behind the iris directly into the anterior chamber of the eye. LPI is the preferred method for managing a wide variety of angle-closure glaucomas that have some degree of pupillary blockage. This laser is most often used to treat an anatomically narrow angle and prevent angle-closure glaucoma attacks.
Two other laser procedures for glaucoma involve reducing the amount of aqueous humor in the eye by destroying part of the ciliary body, which produces the fluid.
With endoscopic cyclophotocoagulation (ECP), the laser probe is placed inside the eye through a surgical incision, so that the laser energy is applied directly to the ciliary body tissue.
Transscleral cyclophotocoagulation uses a laser to direct energy through the outer sclera of the eye to reach and destroy portions of the ciliary processes, without causing damage to the overlying tissues. This treatment is usually reserved for poorly-seeing eyes.
When medications and/or laser therapies do not adequately lower eye pressure and there is a risk of severe vision loss, surgery may be required. The most common of these operations is called a trabeculectomy, which is used in both open-angle and closed-angle glaucoma. In this procedure, a passage is created through the sclera (the white part of the eye) that allows fluid to escape into the space between the sclera and conjunctiva (the outer transparent coat of the eye). A small bubble containing fluid (called a "bleb") forms on the surface of the eye, which is a sign that fluid is draining out. The surgically-created drainage hole has a tendency to close because the body tries to heal the new opening, as if it were an injury. Trabeculectomies are therefore performed using an anti-fibrotic agent that is placed on the eye during surgery. This reduces normal scarring during the healing period. The most common anti-fibrotic agent is Mitomycin-C. Another is 5-Fluorouracil, or 5-FU.
The number of post-operative visits required after a trabeculectomy is variable, and some activities, such as driving, bending and heavy lifting, must be limited for two or three months after surgery.
Drainage Implant Surgery
Several different devices have been developed to aid the drainage of aqueous humor out of the eye to lower IOP. All of these drainage devices share a similar design which consists of a small silicone tube that extends into the eye. The tube is connected to one or more plates, which are sutured to the surface of the eye. Fluid collects over the plate and is then absorbed by the tissues around the eye. This type of surgery usually does not lower IOP as much as a trabeculectomy, but may be required in patients whose IOP cannot be controlled with traditional surgery or who have previous scarring.
Newer nonpenetrating glaucoma surgery (canaloplasty), which does not enter the anterior chamber of the eye, has the advantages of minimizing postoperative complications and lowering the risk for infection. However, such surgery generally does not lower IOP as much as trabeculectomy. It also creates external scarring which may reduce the effectiveness of any future trabeculectomy.
The ExPress mini glaucoma shunt is a stainless steel device that is inserted into the anterior chamber of the eye under a scleral flap. The procedure is similar to a trabeculectomy, but with minimal added benefit.
The Trabectome is a new probe-like device that is inserted into the anterior chamber through the cornea. The probe delivers thermal energy to the trabecular meshwork to open the eye's drainage system through a tiny incision. The resistance to outflow of aqueous humor is thus reduced and as a result IOP is lowered.
Glaucoma is an incurable disease, and lifelong treatment is required to prevent loss of sight.
If you are diagnosed with glaucoma, it is important to follow a regular schedule of examinations to allow your eye doctor to monitor your condition and make sure that your prescribed treatment is effectively maintaining a safe eye pressure.